/*
 * Copyright (c) 2020, 2020, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2020, 2020, Red Hat Inc. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package hello;

// Checkstyle: stop

public class Hello {
    public abstract static class Greeter {
        static Greeter greeter(String[] args) {
            if (args.length == 0) {
                return new DefaultGreeter();
            } else if (args.length == 1) {
                return new NamedGreeter(args[0]);
            } else {
                throw new RuntimeException("zero or one args expected");
            }
        }

        public abstract void greet();
    }

    public static class DefaultGreeter extends Greeter {
        @Override
        public void greet() {
            System.out.println("Hello, world!");
        }
    }

    public static class NamedGreeter extends Greeter {
        private String name;

        NamedGreeter(String name) {
            this.name = name;
        }

        @Override
        public void greet() {
            System.out.println("Hello, " + name + "!");
        }
    }

    public static void main(String[] args) {
        Greeter greeter = Greeter.greeter(args);
        greeter.greet();
        System.exit(0);
    }
}
